I can't import a COLLADA (.DAE) file into my scene
I encountered the exact same issue, and the following steps fixed it for me. I'll be posting the solution for anyone still encountering this issue that comes across this post, like I have.

I originally found this method in this forum post.

Steps to fix: 


Open the .dae file with a text editor. Any will do, but for large enough files, make sure it supports regex find/replace as to not make the fix tedious.
Remove the content of all &lt;diffuse&gt;&lt;/diffuse&gt; tags. Only delete their content, not the tags themselves. 
Save the file as .dae


Example : 

&lt;diffuse&gt;
    &lt;color sid="diffuse"&gt;0.800000  0.800000 0.800000 1.000000&lt;/color&gt;
&lt;/diffuse&gt;


becomes

&lt;diffuse&gt;
&lt;/diffuse&gt;


With regex : 

You can achieve this by replacing &lt;diffuse&gt;[\s\S]+?&lt;/diffuse&gt; with &lt;diffuse&gt;&lt;/diffuse&gt; (add backslashes before / if necessary). 
However, if you have the option to make . include newline, the first regex just becomes &lt;diffuse&gt;.+?&lt;/diffuse&gt;